<button id="disable">disable</button>
<div id="editor"></div>

<script>
	var editor = CKEDITOR.replace( 'editor', {
		skin: 'moono',
		on: {
			instanceReady: function() {
				CKEDITOR.document.getById( 'disable' ).on( 'click', function() {
					editor.setReadOnly( !editor.readOnly );
				} );
			}
		}
	} );
</script>
